I just upgraded to TG4 and noticed if I pause a render (even the default file) I can't restart the render.  I tried using TG3 and renders resume just fine.
My system is a Win10 Pro Ryzen 1800x with 64GB memory.  Not overclocked.  Haven't had any problems with Zbrush, 3D Coat, Lightwave, or benchmarking software, so I'm clueless to what's wrong.  I have  tried changing maximum threads from 64 to 1, but still TG4 locks up.